Feb 7 (Reuters) - U.S. stock index futures were down about a third of a percent, setting Wall Street for a lower open on Wednesday, an almost 2 percent gain in the previous session failing to calm the nerves following the Dow’s biggest intraday fall on Monday.

All three of Wall Street’s main indexes were on course for falls of between 0.2 percent and 0.3 percent, indicated by volatile premarket futures trading.

A wild session on Tuesday saw the Dow Jones Industrial Average swing more than 1,100 points from peak to trough and ended with the benchmark S&P 500 tallying its best day since just before President Donald Trump’s election in 2016.

Traders are bracing for volatility to stay high as they try to figure out if the swings of the past two days are the start of a deeper correction or just a temporary blip in the U.S. market’s nine-year bull run.

The pivotal gauge of S&P 500 volatility, the VIX, opened at a relatively elevated 31 points and was at 28.80. The VIX on Tuesday hit a more than two-and-a-half year high above 50, after trading, on average, below 20 for months.

“It’s over in terms of the severe down move we’ve seen, but reminds us that we’re kind of in an aftershock phase,” said Rick Meckler, president of investment firm LibertyView Capital Management.

“What’s happening now is you’re getting a little bit of struggle between the short-term traders who bought into the dip and are looking to get out before another selloff takes place and people who have gained some confidence that the market’s found a bottom.”

Markets are also on edge over U.S. lawmakers’ wrangling to extend the so-called debt ceiling - funding for the U.S. government runs out on Feb. 8 unless a stopgap bill manages to pass the Senate later on Wednesday.

The S&P 500 remains up 26 percent since Trump’s election, and on Tuesday clawed back into positive territory for 2018, up 0.8 percent.

“It looks like a little bit of a stabilization trade overnight,” said John Brady, senior vice president at futures brokerage R.J. O’Brien & Associates in Chicago.

“I don’t know if it’s over, but a market range maybe established because if you look at S&P e-minis, we’re trading at mid-point of a two-week range, starting back to Jan. 29,” Brady said.

However, some investors fear the market is over-stretched in the context of higher inflation and rising bond yields as central banks withdraw their easy money policies of recent years.

U.S. 10-year yields rose back as high as 2.80 percent after approaching two-week lows around 2.65 percent on Tuesday . They were last trading at 2.79 on Wednesday.

European shares rose around 0.7 percent, while Asian markets were mixed. The recent rout has wiped about $4 trillion off world equities.

Dallas Fed President Robert S. Kaplan said he did not expect the gyrations to have repercussions on the economy and described them as a “healthy” corrections from high valuations.

Among stocks, Walt Disney was up 2.2 percent in premarket trading after the media company’s quarterly profit topped forecasts.

Wynn Resorts climbed 8.6 percent after casino mogul Steve Wynn resigned as the chief executive of his company following sexual misconduct allegations.

Snapchat owner Snap soared 20.6 percent after it reported surging growth in users and revenue in its latest quarter. (Reporting by Tanya Agrawal and Sruthi Shankar; Editing by Arun Koyyur)